Boric acid and borax are used in small quantities for the stabilisation of enzymes in liquid detergents used in both liquid laundry and liquid dishwashing products. The amount of boric acid used in this application was 6,400 tonnes in 2004. This represents approximately 1% of the European market for borates. The major uses of borates include the manufacture of glass (insulation, textile and specialty), ceramics, as a raw material for the manufacture of perborate bleach used in powdered detergents, agriculture, as an essential micronutrient and as a flame retardant in plastics. Borates have been safely used in household cleaning products for nearly a century.
Borates are naturally present and widely distributed in the environment and are essential for the healthy development of all higher plants. They are essential to fish and frogs and there is some evidence to suggest that they are essential to humans. Borates appear to have beneficial uses in animal husbandry.
Boric acid and borax are white crystalline products that readily dissolve in water to form undissociated boric acid and borate anion at high pH. The solubility of borates means that they are widely dispersed and do not bio-accumulate in the environment or in humans.
Boric acid and borax are of low acute toxicity and do not have any genotoxic or carcinogenic potential. The toxicological endpoints of concern arise from feeding studies in laboratory animals and relate to effects on fertility as well as developmental effects at high doses. Possible effects on fertility are indicated by reversible histological effects on the testis, with irreversible effects and a reduction in fertility occurring at much higher doses. Effects on developmental toxicity relate to minor effects on foetal body weight and minor skeletal variations, which, with one exception, had reversed by postnatal day 21. All other effects occurred at maternally toxic doses. Developmental or fertility effects have never been demonstrated in human beings even among population groups with high exposure to borates.
The highest exposure of the general population to borates is through a healthy diet of fresh fruit, vegetables and nuts. Dermal exposure to borates through their use in liquid household cleaning products is low due to the lack of absorption of borates through skin.
The additional contribution to borates from household cleaning products is approximately 2000-6000 times less than normal dietary intake from which it can be concluded that borates pose no risk to human health.
The environmental risks of borates were evaluated by considering exposures resulting from wastewater entering rivers or being used for irrigation and from sewage sludge being applied to agricultural soil. No significant risks were identified.
The amount of borates entering the aquatic environment would be significantly less than associated with historical and current uses of perborate-based cleaning products. The concentrations of borates entering the terrestrial environment would be less than results from agricultural application of borates as plant micro-nutrients. Use of wastewaters for irrigation is presently subject to limitations based on total salinity and from use of perborates; the use of boric acid and borax in liquid detergent applications would not result in unacceptable concentrations. |
